Smoke alarms are prone to dust and dirt build-up after prolonged use. Dust and dirt build-up may cause the smoke alarm to malfunction or give a false alarm.
In the case of a photoelectric detector, the photo chamber must be removed and/or vacuum cleaned to restore the detector to normal operation. The sensors in ionization sensors, must also be vacuumed. Furthermore ionization sensors are also prone to dust and dirt build-up and may cause the unit to false alarm. False alarms in this case result from dirt/dust build-up at or around the center and base electrodes causing a short which will increase the electrode voltage causing the unit to false alarm.
Conductive screens have been used in prior art detectors to exclude bugs or other overly large particulate matter. Prior art screens have also been used to limit air flow into or out of the sensing chamber.
There is a continuing need to address the issues raised by such buildups. It would be desirable to be able to repel dust to eliminate, as much as possible, the build up problem. Given the cost effective nature of residential detectors and the competitive nature of the retail market, no solution which significantly increases detector cost will be successful. Hence, any successful attempt to solve the problem will not only provide a repellant function but will also do so cost effectively.